Phenolic urethane foundry binder

ABSTRACT

The present invention provides a novel phenolic urethane binder composition having a drying oil copolymer in the polyisocyanate resin component. The drying oil copolymers include linseed oil copolymers. The phenolic urethane binders of the present invention are useful in making foundry cores and molds. These foundry binders provide decreased gel formation and improved stability. Foundry mixes prepared using these phenolic urethane binders exhibit improved bench life properties.

FIELD OF THE INVENTION

The present invention relates to a phenolic urethane binder composition having a drying oil copolymer in the polyisocyanate resin component. The phenolic urethane binders of the present invention are useful in making foundry cores and molds.

BACKGROUND OF THE INVENTION

One of the major processes used in the foundry industry for making metal parts is sand casting. In sand casting, disposable foundry shapes, usually characterized as molds and cores, are made by shaping and curing a foundry mix. The foundry mix is a mixture of sand and an organic or inorganic binder. The binder is used to strengthen the molds and cores.

A polyurethane-forming binder system usually consists of a polyhydroxy component (such as a phenolic resin) and a polyisocyanate component, which are mixed with sand to form a foundry mix prior to compacting and curing. Two of the major processes used in sand casting for making molds and cores are the “no-bake” process and the “cold-box” process. In the no-bake process, a liquid curing agent is mixed with an aggregate and shaped to produce a cured mold and/or core. In the cold-box process, a gaseous curing agent is passed through a compacted shaped mix to produce a cured mold and/or core. Polyurethane-forming binders, cured with a gaseous tertiary amine catalyst, are often used in the cold-box process to hold shaped foundry aggregate together as a mold or core.

Among other things, the binder must have a low viscosity, be gel free, remain stable under use conditions, and cure efficiently. In the no-bake process, the foundry mix must have adequate work time to allow the making of core and mold shapes before the foundry mix cures. In the cold-box process, the foundry mix made by mixing sand with the binder must have adequate bench life or the mix will not shape and cure properly. The cores and molds made with the binders must have adequate tensile strengths under normal and humid conditions. Binders which meet all of these requirements are not simple to develop.

The use of polymerized linseed oil in phenolic urethane foundry binders is known. However, these binders suffer from stability issues. Oil-modified polyisocyanates are known to separate and become heterogeneous under normal storage conditions.

Improvements in resinous binder systems which can be processed according to the cold-box or no-bake process generally arise by modifying the binder components, that is, either the polyol part (“part 1”) or the polyisocyanate part (“part 2”). For instance, U.S. Pat. No. 6,365,646, which is incorporated herein by reference, relates to an improved phenolic urethane binder, and a method for improving the humidity resistance of foundry cores and molds made using the improved binder.

It is also known that the part 2 binder component will begin to gel over time on exposure to air. This is most likely due to the isocyanate groups reacting with moisture in the air. Premature gelling of the part 2 binder component is undesirable.

Thus, there is a need for a foundry binder having improved stability relative to known binder materials while attaining improved tensile strength. A foundry binder composition is further needed in which gel formation is suppressed. Additionally, foundry mixes prepared using the foundry binders are needed having improved bench life properties relative to known binders.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, there is provided a phenolic urethane binder composition, including:

-   -   a phenolic resin component;     -   a polyisocyanate resin component comprising a polyisocyanate and         a drying oil copolymer; and     -   a catalyst in an amount effective to cure the resin components.

In a preferred embodiment of the present invention, the drying oil copolymer is a copolymer of linseed oil and dicyclopentadiene.

DETAILED DESCRIPTION OF THE INVENTION

There is provided in accordance with one embodiment of the present invention a phenolic urethane binder having a drying oil copolymer in the polyisocyanate resin component. The drying oil copolymer includes natural oil copolymers such as, for example, linseed oil copolymer.

The phenolic resin component employed in the practice of this invention can vary widely. The phenolic resin component can also be called a part 1 resin component or a part 1 binder component. It may include any phenolic resin which is substantially free of water, that is, contains less than about ⁵% and preferably less than about 1% water, based on the weight of the resin, and which is soluble in the solvents employed, such as phenolic resole or phenolic novolak resins formed by reacting phenolic compounds with aldehydes. Resole or A-stage resins, as well as resitol or B-stage resins, may be made by reacting a molar excess of aldehyde, such as formaldehyde, with a phenolic material in the presence of an alkaline catalyst or metal ion catalysts; the novolak resins may be formed by reacting a molar excess of phenolic component with an aldehyde in the presence of an acid catalyst. Suitable resins are those having benzylic ether bridges between the phenolic rings. A useful phenolic resin component is Sigma Cure 7211 UCB (Part 1) Resin, available from HA-International LLC, Westmont, Ill.

The polyisocyanate component which is employed in a binder according to this invention may likewise vary widely and has a functionality of two or more. Exemplary of the useful isocyanates are organic polyisocyanates such as tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, and mixtures thereof, and particularly the crude mixtures thereof that are commercially available. Other typical polyisocyanates include methylene-bis-(4-phenyl isocyanate), hexane-1,6-diisocyanate, naphthalene-1,5-diisocyanate, cyclopentylene-1,3-diisocyanate, p-phenylene diisocyanate, tolylene-2,4,6-triisocyanate, and triphenylmethane-4,4′,4″-triisocyanate. Higher isocyanates are provided by the liquid reaction products of (1) diisocyanates and (2) polyols or polyamines and the like. Also contemplated are the many impure or crude polyisocyanates that are commercially available. Also useful are polymeric polyisocyanates such as polymethylene polyphenylisocyanate and polyaryl polyisocyanates. The polyisocyanate resin component can also be called a part 2 resin component or a part 2 binder component. The part 2 resin component can optionally include a solvent.

As discussed above, the part 1 resin component and the part 2 resin component may contain solvents and/or plasticizers (hereinafter generally referred to as solvents). The solvents provide component solvent mixtures of desirable viscosity and facilitate coating foundry aggregates with the part 1 and part 2 resin components. While the total amount of a solvent can vary widely, it is generally present in a composition of this invention in a range of from about 5% to about 70% by weight, based on the total weight of the part 1 resin component, and is preferably present in a range of from about 20% to about 60% by weight. With respect to the part 2 resin component, the solvent is generally present in a range of up to about 50% by weight, based on the total weight of the part 2 resin component, and is preferably present in a range of up to about 40% by weight.

The solvents employed in the practice of this invention are generally hydrocarbon and polar organic solvents Such as organic esters or ketones. Typically, the part 1 component may contain a mixture of hydrocarbon and polar solvents, while, typically, the part 2 component may contain hydrocarbon solvents. Suitable exemplary hydrocarbon solvents include aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, high boiling aromatic hydrocarbon mixtures, heavy aromatic naphthas, and the like. A biphenyl compound or a mixture of biphenyl compounds, can be used as an additive per se or as a substitute for a portion or part of the solvents. Kerosene, a mixture of aliphatic and aromatic hydrocarbons, can be used. Kerosene is a common solvent found in urethane binder formulations. Paraffinic oil may also be used and may be any of a number of viscous pale to yellow conventional refined mineral oils. For example white mineral oils may be employed in the present invention. The paraffinic oil may be in the phenolic resin component, the isocyanate component, or both components.

A variety of ester-functional solvents are useful in the part 1 and the part 2 resin components of the present invention. Organic mono esters (long-chain esters), dibasic acid ester and/or fatty acid ester blends increase the polarity of the formulation. Long-chain esters, such as glyceryltrioleate, are also useful in the embodiments of the present invention. The aliphatic “tail” of such an ester is compatible with non-polar components, while the ester “head” of the ester is compatible with the polar components. The use of a long-chain ester thus allows a balancing of polar character which facilitates the incorporation of non-polar component into a more polar system.

Although the solvents employed in combination with either the part 1 resin component or the part 2 resin component do not, to any significant degree, enter into the reaction between part 1 and part 2, they can affect the reaction. Thus, the difference in polarity between a polyisocyanate and a polyol restricts the choice of solvents (and plasticizers for that matter) in which both part 1 and part 2 components are compatible. Such compatibility is necessary to achieve reaction and curing of the binder composition.

The drying oils which are useful in the present invention are glycerides of fatty acids which contain two or more double bonds and can polymerize. Examples of some natural drying oils include soybean oil, sunflower oil, hemp oil, linseed oil, tung oil, oiticica oil and fish oils, and dehydrated castor oil, as well as the various known modifications thereof (e.g., the heat bodied, air-blown, or oxygen-blown oils such as blown linseed oil and blown soybean oil). The above discussion concerning the oils is not intended to imply that such actually cure in the present system by air drying but is intended to help define the drying oils. Also, esters of ethylenically unsaturated fatty acids such as tall oil esters of polyhydric alcohols such as glycerine or pentaerythritol or monohydric alcohols such as methyl and ethyl alcohols can be employed as the drying oil. If desired, mixtures of drying oils can be employed.

The drying oil copolymers of the present invention are copolymers prepared from at least one reactive monomer and a drying oil. Useful reactive monomers include, but are not limited to, olefins such as dicyclopentadiene, cyclopentadiene, maleic anhydride, and the like. A preferred drying oil copolymer is linseed oil copolymer. A useful linseed oil copolymer is DILULIN, which is a copolymer of linseed oil and dicyclopentadiene, available from Cargill, Inc., Minneapolis, Minn.

The amount of the drying oil copolymer employed is generally in a range of from about 0.25% to about 15%, and preferably from about 1% to about 6% by weight, based upon the total weight of the components in the binder composition.

Silanes are commonly added to foundry resin components to improve the adhesion to the sand and the tensile strength of the molds and cores produced from the resin components. Amounts as low as 0.05% by weight, based on the weight of the part 1 or part 2 resin components, have been found to provide significant improvements in tensile strength. Higher amounts of silane can generate greater improvements in strength up to quantities of about 0.6% by weight or more. The silanes are used in a quantity sufficient to improve adhesion between the resin components and an aggregate. Typical usage levels of these silanes range from about 0.1% to about 1.5% based on the weight of the resin component. Useful silanes include 3-aminopropyltriethoxysilane, bis(trimethoxysilylpropyl)ethylenediamine, N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride, secondary amino silane, and the like. Preferred silanes include ureido silane, epoxy silane, and the like. An example of a useful epoxy silane is 3-glycidoxypropyltrimethoxysilane. Inhibitors, or bench life extenders, can be used in the resin components of the present invention. For example, an inhibitor or bench life extender can be added to the polyisocyanate resin component. One useful bench life extender is benzene phosphorus oxydichlioride (“BPOD”).

Generally, the amounts of the phenolic resin component and the polyisocyanate resin component employed in a binder composition of the invention are not critical and can vary widely. However, there should at least be enough of the polyisocyanate resin component present to react substantially completely with the phenolic resin component so that there is no significant unreacted excess of either component present when reaction is complete. In this regard, the isocyanate component is generally in a range of from about 15% to about 400% by weight, based on the weight of the phenolic resin component and is preferably employed in a range of from about 20% to 200%.

As previously indicated hereinabove, the compositions of this invention can be cured by both the cold-box and no-bake processes. In this connection, the compositions include a suitable catalyst. While any suitable catalyst for catalyzing the reaction between the phenolic resin component and isocyanate component may be used, it is to be understood that when employing the cold-box process the catalyst employed is generally a volatile catalyst. On the other hand, where the no-bake process is employed, a liquid catalyst is generally utilized. Moreover, no matter which process is utilized, that is, the cold-box or the no-bake process, at least enough catalyst is employed to cause substantially complete reaction of the components.

Preferred exemplary catalysts employed when curing the compositions of this invention by the cold-box process are volatile tertiary amine gases which are passed through a core or mold generally along with an inert carrier, such as air or carbon dioxide. Exemplary volatile tertiary amine catalysts which result in a rapid cure at ambient temperature that may be employed in the practice of the present invention include trimethylamine, triethylamine, dimethylethylamine, dimethylisopropylamine, and the like.

In general, the process for making a moldable composition, for example a foundry mix, in accordance with this invention, comprises admixing aggregate material such as, for example, sand with at least a binding amount of a phenolic resin component (part 1), a polyisocyanate resin component (part 2) wherein the polyisocyanate has a functionality of two or more, and a sufficient amount of a catalyst to substantially completely catalyze the reaction between the components. The phenolic resin component includes at least one phenolic resin selected from the group consisting of phenolic resole resins and phenolic novolak resins.

The aggregate materials commonly used in the foundry industry include silica sand, construction aggregate, quartz, chromite sand, zircon sand, olivine sand, or the like. Reclaimed sand may also be used.

Sand sold under the product designation F-5574, available from Badger Mining Corporation, Berlin, Wis., is useful in making cores and molds of the embodiments of the present invention. Likewise, sand sold under the product designation Wedron 530, available from Wedron Silica, a division of Fairmount Minerals, Wedron, Ill., is also useful. Sand sold under the product designation Nugent 480, available from Nugent Sand Company, Muskegon, Mich., may also be used. As known in the art, the sand type will affect the strength development of the bound aggregate.

Foundry Cores and Molds. In general, the process for making foundry cores and molds in accordance with this invention comprises admixing aggregate material with at least a binding amount of the part 1 and part 2 binder components. Preferably, the process for making foundry cores and molds in accordance with this invention comprises admixing aggregate material with at least a binding amount of a part 1 binder component of the present invention. A part 2 binder component is added and mixing is continued to uniformly coat the aggregate material with the part 1 and part 2 binder components. In the no-bake process, a sufficient amount of catalyst is added to catalyze the reaction between the components. The admixture is suitably manipulated, as for example, by distributing the same in a suitable core box or pattern. In the cold-box process, a sufficient amount of catalyst is applied to the uncured core or mold to catalyze the reaction between the components. The admixture is cured forming a shaped product.

There is no criticality in the order of mixing the constituents with the aggregate material except where a vaporous catalyst is used, in which case the catalyst is passed through the admixture after it is shaped. On the other hand, it is preferred to add the catalyst, in the case of the no-bake process, as the last constituent of the composition so that premature reaction between the components does not take place. The components may be mixed with the aggregate material either simultaneously or one after the other in suitable mixing devices, such as mullers, continuous mixers, ribbon blenders and the like, while continuously stirring the admixture to insure uniform coating of aggregate particles. It is to be further understood that as a practical matter, the phenolic resole of the part 1 binder component can be stored separately and mixed with solvent just prior to use of or, if desirable, mixed with solvent and stored until ready to use. Such is also true with the polyisocyanate of the part 2 binder component. As a practical matter, the part 1 and part 2 binder components should not be brought into contact with each other until ready to use to prevent any possible premature reaction between them.

When the admixture is to be cured according to cold-box procedures, the admixture after shaping as desired, is subjected to gassing with a vaporous catalyst, such as, for example, an amine catalyst in air. Sufficient vaporous catalyst is passed through the shaped admixture to provide substantially complete reaction between the phenolic resin component and the polyisocyanate resin component to give a cured shaped product. The flow rate of the vaporous catalyst is dependent, of course, on the size of the shaped admixture as well as the amount of binder therein.

In contrast, however, when the admixture is to be cured according to no-bake procedures, the catalyst is generally added in liquid form to the aggregate material with the part 1 binder component. The admixture is then shaped and simply permitted to cure until reaction between the components is substantially complete, thus forming a shaped product such as a foundry core or mold. On the other hand, the liquid catalyst may also be admixed with either the part 1 binder component or the part 2 binder component prior to coating of the aggregate material with the components.

Consequently, by so proceeding, as indicated with an admixture of foundry sand and a binding amount of the phenolic resin component and the polyisocyanate resin component, there can be formed a foundry core or mold including foundry sand and a binding amount of a phenolic urethane binder composition including the reaction product of the phenolic resin component and the polyisocyanate resin component, the polyisocyanate resin component including a polyisocyanate and a drying oil copolymer.

The quantity of binder can vary over a broad range sufficient to bind the refractory on curing of the binder. Generally, such quantity will vary from about 0.4 to about 6 weight % of binder based on the weight of the aggregate and preferably about 0.5% to 3.0% by weight of the aggregate. The binder compositions of this invention may be employed by admixing the same with a wide variety of aggregate materials. When so employed, the amount of binder and aggregate can vary widely and is not critical. On the other hand, at least a binding amount of the binder composition should be present to coat substantially, completely and uniformly all of the sand particles and to provide a uniform admixture of the sand and binder. Thus, sufficient binder is present so that when the admixture is conveniently shaped as desired and cured, there is provided a strong, uniform, shaped article which is substantially uniformly cured throughout, thus minimizing breakage and warpage during handling of the shaped article, such as, for example, sand molds or cores, so made.

In testing embodiments of the present invention, tensile strengths of the cores prepared as noted above were determined using a Thwing-Albert Tensile Tester (Philadelphia, Pa.). This device consists of jaws that accommodate the ends of a “dog-bone-shaped” test core. A load is then applied to each end of the test core as the jaws are moved away from each other. The application of an increasing load continues until the test core breaks. The load at this point is termed the tensile strength, and it has units of psi (pounds per square inch).

The advantages of this invention and its preferred embodiments will be demonstrated more fully by the following Examples, that demonstrate the practice of the invention. In these Examples, parts and percentages are by weight, and temperatures are in degrees Celsius, unless expressly indicated to be otherwise.

Test Cores—Cold-Box Examples. Test cores were prepared by the following method: to a quantity of about 2.5 kg washed and dried aggregate material was added an amount of a part 1 resin component of the present invention and the mixture was stirred for about one minute in a Hobart Kitchen Aid Mixer. Next, a part 2 resin component or a modified part 2 resin component was added to the mixture, which was then further mixed for another two minutes. This mixture was then used to form standard American Foundrymen Society's 1-inch dog bone tensile specimens in a standard core box employing a laboratory core blower. The cores were cured at room temperature using vaporous triethylamine catalyst and the samples were broken at various time intervals after the mix was made. The cores were stored in an open laboratory environment, at ambient temperatures, until tested, or, as noted, the cores were stored in humidity chambers providing a specified humidity. Tensile strength measurements were made as described above. Average values for three tensile strength measurements were typically recorded. The times listed in the tables below for the tensile strength results refer to the core age at the time of testing.

In the testing of cold-box binders, the tensile strength development was determined both as a function of core age and as a function of sand mix age. This latter test is referred to as bench life testing. In bench life testing, a portion of the sand/binder mixture is allowed to age under ambient conditions. At periodic intervals after the mixture has been made, portions of the sand/binder mixture are used to make cores for testing of tensile strength. It is typical that some degradation of tensile strength of a cured core will occur as a function of the age of the sand/binder mixture.

Test cores also can be prepared by the following no-bake method: to a quantity of about 2.5 kg washed and dried aggregate material are added an amount of a part 1 resin component of the present invention, and either a part 2 resin component or a modified part 2 resin component, and a liquid amine catalyst. This mixture is stirred for about one minute in a Hobart Kitchen Aid Mixer and then used immediately to form standard American Foundrymen Society's 1-inch dog bone tensile specimens in a Dietert 696 core box. The cores can be cured at room temperature using a liquid amine catalyst and the samples broken at various time intervals after the mix is made. The cores can then be stored in an open laboratory environment, at ambient temperatures, until tested, or, as noted, the cores are stored in humidity chambers providing a specified humidity. Tensile strength measurements can be made as described above.

The humidity chambers used in the cold-box testing procedure are typical of the type of chambers known in the art. Glass chambers, generally glass dessicators, are used as the humidity chambers. Either water or solutions of water and glycerol are used to generate a relatively constant humidity environment in the glass chambers. Similar chambers can be used in the no-bake testing procedure.

Several polyisocyanate resin components of the present invention were formulated with DILULIN. Table 1 below provides examples of Part 2 binder compositions according to this embodiment (Resins A/DILULIN-E/DILULIN). Table 1 also provides comparative Part 2 binder compositions (Resins A-E). TABLE 1 DILULIN-Modified Polyisocyanate Resin Components Resin Component A A/DILULIN B B/DILULIN C C/DILULIN D D/DILULIN E E/DILULIN Polymeric 75   75   73   73   73   73   80   80   67.5  67.5  Isocyanate Aromatic 10.7  10.7  16.45 16.45 19.7  19.7  13.6 13.6  25.15 25.15 Hydrocarbon Solvent Kerosene 8   8   6.2 6.2 5   5   4   4   3   3   Polymerized 5   — 4   — 1   — 2   — 4   — Linseed Oil DILULIN — 5   — 4   — 1   — 2   — 4   Silane 0.4 0.4 — — 0.4 0.4 — — — — BPOD 0.9 0.9  0.35  0.35 0.9 0.9 0.4 0.4  0.35  0.35

Table 2 below compares the cold storage properties of the polyisocyanate resin components of the present invention with known polyisocyanate resin components. The commercial part 2 resin components each contain polymerized linseed oil as a minor component. TABLE 2 Cold Storage and Viscosity Comparison of DILULIN-Modified Polyisocyante Resin Components Viscosity Cold Storage Cold Storage Resin (cps) Refrigerator, 5° C. Freezer, −12° C. A 25.1 separated separated A/DILULIN 21.1 stable stable B 23.5 separated separated B/DILULIN 18.4 stable stable C 28.8 separated separated C/DILULIN 28.3 stable stable D 22.4 separated separated D/DILULIN 20.4 stable stable

As shown in Table 2, the cold storage advantages of the DILULIN-modified polyisocyanate resin components were clearly demonstrated. Cold storage tests of the commercial part 2 resins were performed until separation was observed. In all cases, the commercial part 2 resins separated after overnight storage, or approximately 24 hours. In contrast, in all cases, DILULIN-modified polyisocyanate resin components provided much improved and unexpected cold storage stability. In all cases, the DILULIN-modified polyisocyanate resin components remained stable for at least 7 days. Certain DILULIN-modified polyisocyanate resin components remained stable for several months at −12° C. Furthermore, the DILULIN-modified polyisocyanate resin components are lower in viscosity than the comparison resin components.

Table 3 below demonstrates the propensity for gel formation of the polyisocyanate resin components of the present invention compared to known polyisocyanate resin components. The resin components were stored at 40° C. to accelerate the gel formation process. TABLE 3 Gel Formation in DILULIN-Modified Polyisocyante Resin Components Resin Observations on Storage at 40° C. A Gel formed in 26 days A/DILULIN No gel in 35 days B Gel formed in 26 days B/DILULIN Gel formed in 26 days, quantity of gel less than Resin B C Gel formed in 7 days C/DILULIN Gel formed in 21 days, quantity of gel less than Resin C D Gel formed in 8 days D/DILULIN Gel formed in 14 days, quantity of gel less than Resin D E Gel formed in 8 days E/DILULIN Gel formed in 8 days, quantity of gel less than Resin E

As shown in Table 3, DILULIN-modified polyisocyanate resin components surprisingly are less prone to formation of insoluble gel. Furthermore, even if the gel developed in the resin component, the quantities of gel formed in DILULIN-modified polyisocyanate resin components were always less than the comparison resin components.

The following specific examples illustrate the present invention. They are not intended to limit the invention in any way. Unless otherwise indicated, all parts and percentages are by weight.

Tables 4 and 5 below demonstrate the performance of a phenolic urethane binder prepared according to the present invention in a sand test, compared to known binders.

Foundry Mix A

-   -   Sand=Badger F-5574 silica sand     -   Binder level=1.0%, based on sand weight     -   Phenolic resin component=Sigma Cure 7211 UCB Part 1 Resin     -   Polyisocyanate resin component=Part 2 Resin A or A/DILULIN         Modified Resin     -   Part 1:Part 2 ratio=55:45

Table 4 compares the performance of Foundry Mix A having DILULIN-modified polyisocyanate resin component to Foundry Mix A with known resin component. TABLE 4 Sand Test Performance of DILULIN-modified Part 2 Resin A A A/DILULIN Time Tensile Strength (psi) Tensile Strength (psi)  1 minute 141 149  1 hour 183 185 24 hours 157 163  2 hours & 72 84 100% Relative Humidity 24 hours & 32 37 100% Relative Humidity  1 hour bench 120 126  2 hour bench 99 114  3 hour bench 69 89 Foundry Mix B

-   -   Sand=Badger F-5574 silica sand     -   Binder level=1.2%, based on sand weight     -   Phenolic resin component=Sigma Cure 7211 UCB Part 1 Resin     -   Polyisocyanate resin component=Part 2 Resin B or B/DILULIN         Modified Resin     -   Part 1:Part 2 ratio=55:45

Table 5 compares the performance of Foundry Mix B having DILULIN-modified polyisocyanate resin component to Foundry Mix B with known resin component. TABLE 5 Sand Test Performance of DILULIN-modified Part 2 Resin B B B/DILULIN Time Tensile Strength (psi) Tensile Strength (psi)  1 minute 265 257  1 hour 333 331 24 hours 344 337  2 hours & 187 180 100% Relative Humidity 24 hours & 102 94 100% Relative Humidity  1 hour bench 242 252  2 hour bench 230 226  3 hour bench 201 218

Sand performance data as shown in Tables 4 and 5 show that the binders made with the DILULIN-modified resin components develop substantial strength and have surprisingly improved bench life profiles compared to known resin components. Unexpected improvement in tensile strength was observed for Foundry Mix A. For 2 and 3 hour bench times, tested tensile strength increased 15 and 29%, respectively. Longer bench life systems are highly valued by foundrymen since such systems can be used for longer periods of time without affecting foundry operations. The foundry mixes made with the DILULIN-modified polyisocyanate resin components of the present invention can be used for longer periods of time. Therefore, foundry mixes made with natural oil copolymer-modified polyisocyanate resin components can be used for longer periods of time. Furthermore, foundry mixes made with drying oil copolymer-modified polyisocyanate resin components can be used for longer periods of time.

The use of a drying oil copolymer surprisingly and unexpectedly results in at least three different improvements over what was known where polymerized linseed oil was used in a phenolic urethane binder system. According to the present invention, part 2 resin components modified with a drying oil copolymer were stable at temperatures as low as −12° C., whereas a part 2 resin component made with polymerized linseed oil was unstable at 5° C. This represents a significant improvement in cold storage temperature. According to the present invention, part 2 resin components made using a drying oil copolymer were surprisingly less prone to gel formation than known part 2 resin components. Gel formation suppression ranged from 6 days to 14 days, while in one case total suppression of gel formation was observed after 11 days. Also, foundry mixes prepared using the drying oil copolymer of the present invention develop substantial strength and have surprising and unexpectedly improved bench life profiles compared to foundry mixes prepared using known resin components. For example, tested tensile strengths for bench times of several hours showed improvements ranging between 15 and 29%. Thus, the differences in properties between the binders of the present invention and known binders have been clearly established. The differences between the binders of the present invention and known binders are clearly unexpected, and the results using the binders of the present invention provide a significant and practical advantage in stability and tensile strength.

There has been disclosed in accordance with the principles of the present invention a phenolic urethane binder including a phenolic resin component; a polyisocyanate resin component having a polyisocyanate and a drying oil copolymer; and a catalyst in sufficient amount to cure the resin components. It has been shown that the drying oil copolymer-modified polyisocyanate resin components are superior to known resin components in cold storage stability. Furthermore, it has been shown that binders of the present invention and foundry mixes made using said binders are superior to known binders and foundry mixes in bench life properties.

Although the above examples are intended to be representative of the invention, they are not intended to limit the scope of the appended claims. It will be apparent to those skilled in the art that modifications may be made therein without departing from the spirit of the invention and the scope of the appended claims. 

1. A phenolic urethane binder composition comprising: a phenolic resin component; a polyisocyanate resin component, the polyisocyanate resin component comprising a polyisocyanate and a drying oil copolymer; and a catalyst in an amount effective to cure the resin components.
 2. The binder of claim 1 wherein the drying oil copolymer is a copolymer of linseed oil and dicyclopentadiene.
 3. The binder of claim 1 wherein the catalyst is a tertiary amine.
 4. A foundry mix comprising sand and the phenolic urethane binder of claim
 1. 5. The foundry mix of claim 5 wherein the binder is present in an amount ranging from about 1% to about 10% based on the weight of the sand.
 6. The binder of claim 2 wherein the catalyst is a tertiary amine.
 7. A foundry mix comprising sand and the phenolic urethane binder of claim
 2. 8. The foundry mix of claim 7 wherein the binder is present in an amount ranging from about 0.4% to about 6% based on the weight of the sand.
 9. The binder of claim 2 wherein the linseed oil-dicyclopentadiene copolymer is present in an amount ranging from about 0.25% to about 7.5% based on the total weight of the binder.
 10. The binder of claim 2 wherein the linseed oil-dicyclopentadiene copolymer is present in an amount ranging from about 1% to about 6% based on the total weight of the binder.
 11. The binder of claim 1 wherein the drying oil copolymer is a natural oil copolymer.
 12. A curable phenolic urethane binder, comprising: a phenolic resin in an amount ranging from about 15% to about 40% based on the total weight of the binder; a polyisocyanate in an amount ranging from about 15% to about 40% based on the total weight of the binder; and a copolymer of linseed oil and dicyclopentadiene in an amount ranging from about 0.25% to about 7.5% based on the total weight of the binder.
 13. A foundry mix comprising sand and the curable phenolic urethane binder of claim 12 in an amount ranging from about 0.4% to about 6% based on the weight of the sand.
 14. A resin component composition for use in a foundry binder, comprising: a polyisocyanate; and a drying oil copolymer.
 15. The resin component composition of claim 14 wherein the drying oil copolymer is a copolymer of linseed oil and dicyclopentadiene.
 16. The resin component composition of claim 14 wherein the drying oil copolymer is a natural oil copolymer.
 17. A foundry core or mold made using the binder composition of claim
 1. 18. A foundry core or mold made using the binder composition of claim
 2. 